Position, navigation, and timing (PNT) systems operate by estimating parameters such as time-of-arrival (TOA) and direction-of-arrival (DOA) of received signals. A common technique for achieving precision PNT estimation is for the PNT receiver to perform a correlation for a known reference signal. It is noted, however, that precision PNT estimation may be limited in the presence of multipath.
Multipath refers to a propagation phenomenon that results in radio signals reaching a receiving antenna by two or more paths. In the presence of multipath, precision PNT estimation can be limited by the side-peaks of the correlation function. For instance, for signals with rectangular or near-rectangular spectra, the first correlation side-peaks can be as large as 13 dB below the main peak. Side-peaks only fade away slowly as correlation lag increases.
While the correlation side-peaks may be reduced by altering the transmitted signal, altering the transmitted signal may have undesirable consequences on other aspects of system performance. For example, if the signal is also used for communications purposes, altering the transmitted spectrum could seriously degrade data link performance.
Therein lies a need for systems and methods for mitigating multipath effects on precision PNT estimation without the aforementioned shortcomings.